the b43 driver has not attached to your NIC.
linuxwireless.org says b43 has been tested on a bcm4312 that has pciid 14e4:4315 ; lspci -v gives

Quote:

Broadcom Corporation Device 04b5

suggesting that your chipset may not be the supported chipset. run lspci -nnk and see if [14e4:4315] appears on either the Network controller or Subsystem line. If no [14e4:4315] appears, what is inside [] for your NIC? Look at the end of dmesg for b43, ssb, 80211, and wlan0. for any entries that may explain what happened. you may need to run

Ensure that you have BCMA_HOST_PCI enabled in your kernel, and firmware is installed.
Also wireless-tools / iwconfig don't support modern nl80211 based drivers. So you need to either enable the wireless extension compatibility, or use net-wireless/iw